The present invention relates generally to rivet setting machines and more particularly to self-piercing rivet setting machines for connecting two or more panel members (or a panel and a component), for example, in an automobile assembly operation.
Rivet setting machines are widely used in a variety of applications to attach two or more components or workpieces together such as aluminum panels in automobile assemblies. More specifically, self-piercing rivet setting machines are preferably employed to connect workpieces without penetrating or piercing interior surfaces thereof in order to improve sealing performance. Generally, a self-piercing rivet is deformed into the workpieces using a punch and die combination, wherein an annular edge of the rivet shank is deformed into and along with the workpieces that are fastened together.
One example of a self-piercing rivet is disclosed in U.S. Pat. No. 5,752,305 to Cotterill et al. (corresponding to Japanese Patent Laid-Open No. 08-505087). The self-piercing rivet, as illustrated in FIG. 1, comprises a flange-shaped head and a pair of legs extending downward from the head. When the rivet is driven into workpieces, e.g. a pair of automobile body panels, by use of a punch and a die, the legs are deformed to spread out their front ends while piercing the panels, and thus the panels are connected to each other by the spreadingly deformed legs and the head. The self-piercing rivet is suitable for connecting aluminum body panels to which welding processes are not applied. Since the aluminum bodies are increasingly employed to provide weight reduction in automobile bodies, the demand for the self-piercing rivet would similarly increase.
A rivet setting machine of the known art that installs self-piercing rivets is disclosed in EP 0 893 179 B1 to Mauer et al., (corresponding to Japanese Patent Laid-Open No. 11-90575). As shown in FIG. 2, the self-piercing rivet setting machine comprises a C-shaped frame including a horizontal upper arm, a vertical arm and a horizontal lower arm. The machine further comprises a punch movably mounted on one end (the end of the horizontal upper arm) of the C-shaped frame and formed to hold the self-piercing rivet. Additionally, a die is disposed at the other end (the end of the horizontal lower arm) of the C-shaped frame to receive the self-piercing rivet that is held in the punch. Furthermore, the machine comprises a drive means, such as a motor, for pressing the punch against the die to urge the self-piercing rivet against the die, whereby a plurality of workpieces placed between the punch and the die are fastened together. Particularly, in the self-piercing rivet setting machines described in the known art, the legs of the self-piercing rivet are adapted to connect the workpieces to each other without penetrating or piercing the workpieces so that high sealing performance to the interior of the automobile can be advantageously maintained.
Self-piercing rivet setting machines usually include the C-shaped frame comprising the horizontal upper arm, the vertical arm, and the horizontal lower arm. Further, the C-shaped frame is formed in a one-piece unit to withstand the loads induced when fastening the rivet to the workpieces. Thus, when the rivet setting machine is not operated, the distance between the punch mounted on the one end (e.g. the end of the horizontal upper arm) and the die disposed at the other end (e.g. the end of the horizontal lower arm) is arranged to be constant and is therefore limited due to the size of the C-shaped frame. If the workpieces are simple flat plates, the workpieces are positioned relatively easily between the punch and the die.
However, if a workpiece has a standing wall protruding at a right angle therefrom, it may be impossible to position the workpiece between the punch and the die. In such a case, it is necessary to change the C-shaped frame with a larger one in order to increase the distance between the punch and the die, however, a large C-shaped frame that has a sufficient stiffness to withstand the loads leads to a larger rivet setting machine as a whole. Further, in conjunction with an upper limit in the stroke of the punch of the rivet setting machine, it is impractical to change the drive unit and other related parts. As a result, some workpieces have not been able to be fastened together due to their large shape and complex configurations.
Accordingly, there remains a need in the art for a rivet setting machine that can accommodate larger and more complicated workpieces without removing and replacing features, such as a C-shaped frame, of the rivet setting machine. The rivet setting machine should further be capable of accommodating larger and more complicated workpieces at high production rates.
In accordance with the present invention, a rivet setting machine includes a die supporting member that is movably mounted to a frame. The die supporting member holds a die in a first position, wherein the die is placed in an opposed relationship to a punch during fastening operations. The die supporting member further holds the die in a second position, wherein the die is placed at a position apart from the punch, thereby increasing the distance between the die and the punch during non-fastening operations. As a result, additional working space is provided for inserting and removing larger and more complicated workpieces.
In one form, the die supporting member is movably mounted to the frame using a pin. Accordingly, the die supporting member is pivoted about the pin between the first and second positions. In another aspect of the present invention, the die supporting member is automatically pivoted using a rod extending from a drive unit. The drive unit is mounted to the frame, and the rod is attached to the die supporting member such that the drive unit operates to retract and extend the rod, thereby pivoting the die supporting member about the pin between the first position and the second position. In yet another form, the die supporting member is movably mounted to the frame using a rail.
The present invention is advantageous over conventional devices since the distance between the punch and the die of the present invention is increased even further to accommodate even larger and more complicated workpieces. In addition, the die supporting member similarly includes a positioning guide that properly positions the die in the first position during fastening operations. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.